Error preventing means for flash synchronized photography

ABSTRACT

Error preventing means for focal-plane synchronized camera shutters to inhibit the operation of an electronic flash unit when inadvertently connected to a focal-plane flashbulb outlet, and alternatively for inhibiting the operation of flash bulbs inadvertently connected to an electronic flash outelt, includes a voltage limited short circuiting resistance element which is connected in parallel with a synchronizing switch in the trigger circuit for a flash bulb, and in series with a synchronizing switch of the trigger circuit for an electronic flash unit.

United States Patent [191 Tokutomi ERROR PREVENTING MEANS FOR FLASHSYNCHRONIZED PHOTOGRAPHY [75] Inventor: Seijiro Tokutomi, Kanagawa-ken,Fujisawa, Japan [73] Assignee: Asaki Kogaku Kogyo Kabushiki Kaisha,Tokyo-to, Japan [22] Filed: June 29, 1972 [21] Appl. No.: 267,636

[30] Foreign Application Priority Data July 20, I97! Japan 46/63470(utility model) [52] U.S. Cl 95/ll.5 R, 95/10 L [51] Int. Cl. G03b 15/02[58] Field of Search 95/1 1.5 R, 11 L [56] T References Cited UNITEDSTATES PATENTS 3,504,602 4/1970 Kiperetal. "95/115 [451 Aug. 14, 19733,307,462 3/1967 Hutchison, Jr. et al 95/11 L Primary Examiner-Robert P.Greiner Attorney-Robert A. Buckles et al.

[ 5 7] ABSTRACT Error preventing means for focal-plane synchronizedcamera shutters to inhibit the operation of an electronic flash unitwhen inadvertently connected to a focal-plane flashbulb outlet, andalternatively for inhibiting the operation of flash bulbs inadvertentlyconnected to an electronic flash outelt, includes a voltage limitedshort circuiting resistance element which is connected in parallel witha synchronizing switch in the trigger circuit for a flash bulb, and inseries with a synchronizing switch of the trigger circuit for anelectronic flash unit.

6 Claims, 3 Drawing Figures Patented Aug. 14, 1973 3,752,048

ERROR PREVENTING MEANS'FOR FLASH SYNCHRONIZED PHOTOGRAPHY BACKGROUND OFTHE INVENTION tense lightbut of shorter flash duration. The electronicflash also requires different'timing in the internal synchronizingcircuits of the camera as thistype of flash must not be triggereduntilthe focal-planeshutteris all the way open. Thisis commonly knownasX synchronization. Some camerasproviding bothtypes ofsynchronization'have separate flash connector terminals,-one labeled FFand the other labeled X, whileother-cameras may have but a singleexternal-flash connector socket with a selector switch-mounted on"thecamera body and moveableeither toFPorX positions depending on thetype'of synchronization desired.

Problems may arise, howevenif the photographer inadvertently connectshis 'flash equipmentto the wrong terminal, or ifhe'inadvertentlyleaves'the synchselector in the wrong position, andthis can easilyoccurin the case of a busy .photographer who may 'altematively use flashbulbs for one type of picture 'and'electronic flash for other shots. Theproblem .in such cases is that the flash equipmentitself may operate,ableit not necessarily in propersynchronism with'the camera shutter,andthe photographer may shoot a whole sequence of pictures withoutrealizing that his shutter andflash are not synchronizing, simplybecause he sees the flash I go off when he presses the shutter release.

OBJECTS OF THE INVENTION The principal object of't he invention is toprovide fool-proof means for assuring photographersthattheir photoflashequipment is properly connected to their cameras.

Alternatively an objectofthe inventionis to provide means for inhibitingand preventing .the operation of either flash bulbs 'or electronic flashunits unless the correct synchronizing "connections have been made atthe camera.

Other objects of the invention will in .part-beobvious BRIEF DESCRIPTIONOF THE DRAWING FIG. 1 is a schematic circuit diagram of the simplestform of the invention for use in cameras having separate FF and Xsynchronizing terminals;

FIG. 2 is a schematic circuit diagram similar to FIG. 1 but illustratingan improved embodiment of the invention; and

FIG. 3 is a schematic circuit diagram of an alternative embodiment ofthe invention illustrated in FIG. 1 and -FIG.2, and especially useful incameras provided with but a single flash synchronizing tenninal foreither FF or X synchronization.

Similar reference characters refer to corresponding parts in all threefigures of the drawing.

DETAILED DESCRIPTION Referring now in greater detail to FIG. l of thedrawing'a flash synchronizing terminal connection 1, which commonly maybea co-axial connector socket mounted on an external portion of a camerabody, is provided forthe connection of an electronic flash unit and isdesignated as the X terminal. A similar synchronizing-terminal 2 is alsoprovided on the camera body for connection to a flash bulb holder (forFF type flash bulbs) and is designated as the FP terminal. Asynchronizing switch 3 internally of the camera and operated by theshutter is connected in series with a voltage regulator element 5between one side of the X and FF terminals l and 2 for the triggering ofelectronic flash units connected thereto. The voltage regulator elementS-has a predetermined threshold value which may be, forexample 25 volts,which is sufficiently lowwith respect tothe voltage of theextemalelectronic flash unit (not shown)-that it is fully conductive when thesynchronizing switch 3 is'closed. Thus, this synchronizing circuit ofFIG. 1 causes the electronic flash to operate when such flash equipmentis connected to terminal 1.

Still referring'to FIG. 1, synchronizing switch 4 is connected acrossthe conductors of PP terminal 2 and in .parallel with a resistor'6 whichmay be of the value of approximately 100 KO. The outerconductors of theX and FF synchronizing terminals 1 and Zare grounded to the camera bodyas indicated'in FIG. '1. Operation of the "synchronizing switches 3 and4 is controlled by connection with the camera shutter mechanism (notshown) in such manner that switch 4'is first closed and subsequentlythereto (in a matter of microseconds as determined by the shutter speed)switch 3 is closed. When the synchro-cord of an electronic 'flash unitis connected as it should be to the X synch terminal 1, closure first ofswitch 4 and thereafter of switch 3 completes acircuit through voltageregulator 5 to fire the electronic flash at the moment switch 3 closes,when the camera focal-plane shutter is fully open. However, if thephotographer has inadvertently and erroneously connected his electronicflash cord to the FP terminal 2, then the power source of the electronicflash unit is dissipated through resistor 6 and the electronic flashdoes not go off, so that the photographer immediately realizes thatsomething is awry and thereby discovers his erroneous connection ofthesynch cord.

Alternatively, still referring to FIG. 1 of the drawing, if thephotographer is using flash bulbs as distinguished from electronic flashand he inadvertently or erroneously connects his synch cord to the Xterminal 1 instead of to the FP terminal 2 as should be done in thiscase, then the power supply of the external flash gun (not shown) whichis of lower voltage than the operating threshold of voltage regulator 5is unable to complete a firing circuit therethrough and consequently theflash bulb does not operate even though switches 3 and 4 are both closedby the camera shutter action. Upon noting the failure of the bulb toflash the photographer discovers his erroneous connection and may thencorrectly connect the synch cord to the FP terminal 2. With the properconnection of flash gun to FF terminal 2, resistor 6 is of such a highimpedance that it imposes no drain upon the flash bulb power souce, andconsequently the flash bulb fires immediately upon closure of switch 4at the start of the camera shutters opening action.

Reference is now had to FIG. 2 of the drawing which discloses animprovement over the circuit of FIG. 1, requiring only the addition of asecond voltage regulator element 7. A possible drawback or inconveniencewith the circuit of FIG. 1 is that when the synchro-cord of anelectronic flash unit is erraneously connected to the FP terminal 2, thecurrent drain through resistor 6 (which prevents the electronic flashfrom operating in this case) may at least temporarily exhaust the powersupply of the electronic flash unit, thereby causing an undesirabledelay in recharging time before the elec- J tronic flash may be operatedwhen properly connected thereafter to X terminal 1. By inserting voltageregulator element 7 in series with resistor 6, element 7 being ofcorresponding characteristics to element 5, the voltage drop across 6and 7 is sufficient to inhibit and prevent the electronic flash unitfrom firing, while the current drain upon the electronic flash unitspower supply is very substantially diminished. Otherwise the operationof the embodiment of FIG. 2 is the same as described above withreference to FIG. 1.

Reference is now made to FIG. 3 of the drawing which may be considered apreferred embodiment of the invention, atleast to the extent that itprovides but a single flash connector terminal 8 into which may beconnected either electronic flash units or flash bulb equipment. A twoposition selector switch 9 mounted on the camera body is manuallyoperable by the photographer into either Fl of X synch positions asshownin FIG. 3. The internal shutter operated synchronizing switches 3and 4 correspond to the same elements in FIG. 1 and FIG. 2, and areoperated in the samesequence described above. Similarly voltageregulator 5 and resistor 6 correspond to and operate the same as thecorresponding elements described in FIG. 1 and FIG. 2. Errors made bythe photographer in the positioning of switch 9 cause the same circuitstates as those caused by the reverse synehrocord connectionsaforementioned with reference to FIG. 1 and FIG. 2, so that the userbecomes immediately aware of his error and can take prompt correctiveaction to avoid ruining.

quite inexpensive,- and the circuit interconections are simple, theinvention can be easily incorporated into cameras for substantiallygreater convenience and reliability of photography by flash.Furthermore, it is easily possible to add visual display means in theform of a miniature lamp operable by current produced in the circuit dueto reverse synchro-cord connection or erroneous positioning of thechange-over switch. Additionally, if desired, a safety switch may beprovided to keep the synchronizing circuit for the electronic flash tubenormally open at all times except during the interval of shutterrelease.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawing shall be interpreted as illustrative and not in a limitingsense.

It is also to be understood that the following claims are intended tocover all of the generic and specific fea tures of the invention which,as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

l. Photographic flash inhibiting means for preventing the firing ofeither flash bulbs or electronic flash tubes when either form of flashequipment is erroneously connected to the wrong synchronizing circuit ofa camera, comprising in combination a first camera connector forconnection to flash bulbs and a second camera connector for connectionto electronic flash tubes, a first synchronizing switch for operatingflash bulbs connected to said first camera connector and a secondsynchronizing switch for operating electronic flash tubes connected tosaid second camera connector, said first and second switches controlledby the camera shutter to close successively in sequential order as theshutter opens, voltage dropping conductive means connected across saidfirst camera connector and in parallel with said first synchronizingswitch whereby an electronic flash if connected to said firstconnectoris effectively short circuited by said voltage dropping means,and voltage limited regulating means connected in series with saidsecond synchronizing switch between said first and second cameraconnectors whereby a flash bulb if connected to said second connector isprevented from operating by said voltage'limited regulator meansdropping the voltage below the required threshold value.

2. The combination of claim 1 wherein said voltage dropping conductivemeans comprises a fixed resistance, and said voltage limited regulatingmeans comprises a zener diode.

3. The combination of'claim 1 wherein said voltage dropping conductivemeans comprises a fixed resistance in series with a zener diode.

p 4. Error preventing means for flash synchronized photography wherein aselector switch movable to first and second positions is provided forconditioning a flash connector to operate with flashbulbs in the firstposition and with electronic flash in the second position, a firstsynchronizing contact switch is connected to saidselector switch in itsfirst position for triggering a flashbulb circuit connected thereto anda second synchronizing contact switch is connected to said selectorswitch in its second position for triggering an electronic fromoperating when said selector switch is in its second position. a

5. The combination of claim 4 wherein said voltage dropping currentconductive element comprises a fixed resistor in series with at leastone zener diode.

6. The combination of claim 4 wherein said threshold voltage limitedconductive element comprises a pair of zener diodes connected back toback.

- I t i i

1. Photographic flash inhibiting means for preventing the firing ofeither flash bulbs or electronic Flash tubes when either form of flashequipment is erroneously connected to the wrong synchronizing circuit ofa camera, comprising in combination a first camera connector forconnection to flash bulbs and a second camera connector for connectionto electronic flash tubes, a first synchronizing switch for operatingflash bulbs connected to said first camera connector and a secondsynchronizing switch for operating electronic flash tubes connected tosaid second camera connector, said first and second switches controlledby the camera shutter to close successively in sequential order as theshutter opens, voltage dropping conductive means connected across saidfirst camera connector and in parallel with said first synchronizingswitch whereby an electronic flash if connected to said first connectoris effectively short circuited by said voltage dropping means, andvoltage limited regulating means connected in series with said secondsynchronizing switch between said first and second camera connectorswhereby a flash bulb if connected to said second connector is preventedfrom operating by said voltage limited regulator means dropping thevoltage below the required threshold value.
 2. The combination of claim1 wherein said voltage dropping conductive means comprises a fixedresistance, and said voltage limited regulating means comprises a zenerdiode.
 3. The combination of claim 1 wherein said voltage droppingconductive means comprises a fixed resistance in series with a zenerdiode.
 4. Error preventing means for flash synchronized photographywherein a selector switch movable to first and second positions isprovided for conditioning a flash connector to operate with flashbulbsin the first position and with electronic flash in the second position,a first synchronizing contact switch is connected to said selectorswitch in its first position for triggering a flashbulb circuitconnected thereto and a second synchronizing contact switch is connectedto said selector switch in its second position for triggering anelectronic flash circuit connected thereto, comprising in combination avoltage dropping current conductive element connected in parallel withsaid first synchronizing contact switch whereby an electronic flash isprevented from operating when said selector switch is in its firstposition, and a threshold voltage limited conductive element isconnected in series with said second synchronizing contact switchwhereby a flashbulb is prevented from operating when said selectorswitch is in its second position.
 5. The combination of claim 4 whereinsaid voltage dropping current conductive element comprises a fixedresistor in series with at least one zener diode.
 6. The combination ofclaim 4 wherein said threshold voltage limited conductive elementcomprises a pair of zener diodes connected back to back.